The reduction in size of electronic devices creates a need to minimize off chip circuitry components to reduce component cost and required board size. One of the larger elements typically required in a power supply for electronic devices is an inductor. When a device has multiple loads which have different power requirements, there are two typical options: use multiple power drivers which require multiple inductors, or find a way to use a single inductor for multiple loads.
Single Inductor Multiple Output (SIMO) power supplies have been developed to meet the needs of multiple voltage based loads. For example, a SIMO supply may have a 1.6V, 3.3V, and 5V output driven from a single inductor. Not all loads, however, are voltage dependent. An example of this is a string of light emitting diodes (LEDs). An LED is a current based device which can have a different forward voltage from device to device. A voltage regulated power supply is less than ideal for this type of load. Dimming LEDs generally requires the current supply to be rapidly turned on and off using a pulse width modulation technique. It would be desirable to have a multiple output power supply which could regulate a variety of load types and dim the outputs by pulse width modulation.